Gasoline compositions have traditionally been formulated to improve the performance of carburetor and throttle body injected engines. Beginning in about 1984, electronic port fuel injected engines were commonly introduced by automobile manufacturers. Shortly thereafter, in about 1985, problems began to be reported with intake valve deposits in electronic port fuel injected engines characterized by hard starting, stalls, and stumbles during acceleration and rough engine idle.
Accordingly, it would be desirable to have fuel compositions which reduced or eliminated such undesirable intake valve deposits in electronic port fuel inJected engines. Also, since some carburetor and throttle body injector engines will still be in use for the foreseeable future, it would be desirable if such fuels could also be compatible with these engines. Intake valve detergency is generally defined by the BMW NA standard of intake valve cleanliness for unlimited mileage, which is an established correlation of driveability and intake valve deposit weight of 100 milligrams or less.
Oil-soluble polyalkylene polyamines containing an olefinic polymer chain are known to improve detergent properties of fuels used in carburetor and throttle body type engines.
U.S. Pat. No. 3,756,793 discloses fuel compositions containing minor amounts of (1) a polyamine reaction product of a polyisobutenylchloride with an average molecular weight between 600-2500 and certain alkylene polyamines and (2) an organic substance with a viscosity between 20 and 2500 centistokes at 20.degree. C. which is a polymer or copolymer or mixture thereof of hydrocarbons and hydrocarbons containing oxygen or oxygen and nitrogen. While it is stated at column 4, lines 59-61, that each additive can be present in the fuel at 0.001 to 0.1% w, the examples all illustrate only a polyoxypropylene glycol as (2) and the ratio by weight of (1) to (2) of 0.25 (Example I), and 0.29 (Example II). These fuels are described for only carburetor-type engines.
U.S. Pat. No. 4,357,148 discloses gasoline compositions containing (1) certain alkylene polyamines and (2) certain oil-soluble olefin polymers and copolymers. At column 5, lines 9-11, the concentration of the polyamine (1) is said to be about 6 to about 600 ppm and at column 2, line 35, that the concentration of the olefin (co)polymers (2) is 250-1200 ppm. In the examples the ratio of polyamine as basic nitrogen (1) to olefin (co)polymer as ppmw (2) is 0.00125 (Examples I-IV and VI), 0.005 (Example V), and 0.0015 (Example VII). The gasoline is only described for use in carburetor-type engines.
U.S. Pat. No. 3,438,757 discloses fuels containing certain hydrocarbylamines and polyamines. Minor amounts of certain nonvolatile lubricating mineral oils can be added to the gasoline. These additives were believed to act as carriers for the detergent in carburetor engines and to assist in removing or preventing deposits. However, the ratios of detergent to carrier in the table are only 0.05 to 0.125.
U.S. Pat. No. 4,022,589 discloses fuels containing a polybutene amine detergent and a larger amount of a solvent-refined paraffinic lubricating oil. These fuels are not disclosed for port fuel injected engines.
European patent 290,088, which corresponds to allowed U.S. patent application Ser. No. 190,196, now U.S. Pat. No. 4,846,848 discloses gasoline containing polyalphaolefin to reduce valve sticking in carburetor engines and its optional use with other additives, e.g., polyamines, in gasolines where the polyalphaolefin is the major additive. Use with electronic port fuel injected engines is not disclosed.
Such compositions, where the detergent is illustrated as a minor ingredient as compared to a second component oil, glycol, polymer or the like, have reduced effectiveness in electronic port fuel injected engines where the second component appears to act like a diluent, reducing the effectiveness of the detergent, which it had enhanced in carbureted engines. Accordingly, new unleaded fuel compositions are needed for the efficient operation of the new electronic port fuel injected engines.